The conventional practice for furnishing three-dimensional patterns, including indicia, characters, designs, or combinations thereof (hereinafter collectively referred to as "patterns"), on surfaces of injection molded articles typically comprises using an engraved mold whose surfaces have been carved or engraved to form a reverse pattern image--i.e. a pattern image which is reverse to the pattern ultimately formed on the surface of the injection molded article. However, engraved molds tend to be expensive due to the engraving that is required. In addition, engraved molds usually take a long time to make. These factors usually mitigate against the use of such molds when a small number of molded articles are intended to be produced. Therefore, a more inexpensive and relatively easier process for furnishing three-dimensional surface patterns on injection molded articles has been needed. It is towards satisfying such a need that the present invention is directed.
The present invention relates to processes whereby three-dimensional patterns may be formed on surfaces of injection molded articles. More specifically, the present invention relates to forming three-dimensional patterns on surfaces of injection-molded articles using a master film of thermoplastic resin which has excellent heat-resistance strength and rigidity properties and which is provided with a reverse image of the three-dimensional pattern to be formed on the injection molded article. The three-dimensional pattern on the thermoplastic master film is transferred to the injection molded article by first placing the film in the mold cavity of an injection mold and then injecting molten thermoplastic resin into the mold cavity. In such a manner, the surface of the three-dimensional pattern provided on the master film will come into contact with the molten thermoplastic resin being injected into the mold cavity so that, upon cooling and solidification, the three-dimensional pattern will be formed in the surface of the injection molded article.
These aspects, as well as others, will become more clear after careful consideration is given to the detailed description of the preferred exemplary embodiments thereof which follow.